N,n-dialkylalkanolamines

ABSTRACT

Certain dialkylaminoalkylurethanes, formed by the reaction of isocyanates with certain N,N-dialkylalkanolamines, are used as latent catalysts for the cross-linking or trimerization of polyisocyanate-terminated prepolymers.

United States Patent [1 1 Rice [ N,N-DIALKYLALKANOLAMINES [75] Inventor:David E. Rice. Woodbury, Minn.

[73] Assignee: Minnesota Mining and Manufacturing Company, St. PaulMinn.

[22] Filed: Oct. 9, I973 (21] Appl. No.: 404,323

Related US. Application Data [62] Division of 561" Nd 24l,4l3 April 5.[972. Pat. No.

[ July 22, 1975 Windcmuth et al. .i 260/47! C Carlick et al. 260/47l ClO/l973 l/l974 Primary ExaminerR0bert Gerstl Assislanl Examiner-L. A.Thaxton Attorney Agent, or FirmAlexander, Sell, Steldt & DeLaHunt [57}ABSTRACT Certain dialkylaminoalkylurethanes, formed by the reaction ofisocyanates with certain N N- dialkylalkanolamines. are used as latentcatalysts for the crosslinking or trimerization ofpolyisocyanateterminated prepolymers.

6 Claims, N0 Drawings 1 N,N-DIALKYLALKANOLAMINES This is a division ofapplication Ser. No. 241,413 filed Apr. 5, 1972 now US. Pat. No.3,786,030.

This invention relates to a process for trimerizingisocyanate-terminated urethane prepolymers to produce cross-linkedpoly(isocyanurate-urethanes). In a further aspect, it relates tocatalysts useful in trimerizing isocyanate-terminated urethaneprepolymers and to a method of making said catalysts.

The trimerization of aliphatic or aromatic isocyanates to produceisocyanurates is well known. A host of trimerization catalysts have beendisclosed, used, or patented (see, Polyurethane: Chemistry andTechnology, Part 1, by J. H. Saunders and K. C. Frisch, lntersciencePub, New York (1962), page 94 and US. Pat. Nos. 2,979,485, 2,954,365,2,978,449 and 3,211,703). The trimerization of isocyanates isparticularly of interest in urethane polymer chemistry to producepo1y(isocyanurate-urethane). The isocyanurate moieties in thepoly(isocyanurate-urethane) impart temperature stability and hydrolyticstability and the urethane moieties impart toughness and shockresistance to the cured resin.

Though many of the catalysts disclosed in the abovedescribed prior artprocesses have merit, they also have undesirable features. For example,prior art tertiary amine catalysts are active at room temperature andhigher temperatures. However, in some applications involvingtrimerization to form cross-linked polyisocyanurate polymers, it isdesirable that the curing reaction take place rapidly at elevatedtemperatures but proceed very slowly at room temperature in order toprovide systems with extended pot life at ambient room temperatures. Insome cases, a resin system which cures very quickly at room temperaturecreates processing problems when used and restricts the amount of resinwhich can be mixed at one time. Where the resins cure rapidly at anelevated temperature, however, processing is simplified and a fullycuredpoly(isocyanurateurethane) can be quickly produced.

Co-catalyst systems composed of a urethane compound and a separatetertiary amine compound for preparation of polyisocyanurates have beendisclosed (see US. Pat. No. 2,954,365). These co-catalyst systems mayuse, as a catalyst component, urethanes consisting of one molofN,N-dialkylaminoethanol and one mol of phenyl isocyanate, or one molof N- alkyldiethanolamine and two moles of phenyl isocyanate; however,these systems have poor room tempera ture latency and in some cases thereaction mixture must be diluted or cooled to control the trimerizationof isocyanate at ambient temperatures. Generally, those prior artsystems which do not cure rapidly at room temperature also do notprovide for a markedly accelerated cure at elevated temperatures.

Briefly, it has been discovered that dialkylaminoalkylurethanes arelatent catalysts at room temperature but active catalysts at elevatedtemperatures for the trimerization of isocyanate-terminated urethaneprepolymers. Said catalysts can be prepared by reacting certaindialkylalkanolamines with isocyanate-terminated urethane prepolymers.

The isocyanate terminated prepolymers used to form the catalysts ofthisinvention are known (see, US. Pat. No. 3,054,755) and are generallyprepared by reacting an excess of polyisocyanate, such as an aromaticdiisocyanate, with polyalkyleneether polyols or polyester polyols.Broadly, said NCO-terminated prepolymers have the structure:

where Y, is the hydroxyl-free residue ofa polyol having a plurality ofhydroxyl groups, R' is the residue of a polyisocyanate precursor used tomake the isocyanateterminated prepolymer, p is equal to q-l where q isthe number of isocyanate moieties of said polyisocyanate, and z is thenumber equal to the functionality or hydroxyl groups of said polyol.Generally, p will be an integer from 1 to 4, preferably 1 to 2, and 2will be an integer from 2 to 6, preferably 2 to 4.

The polyol component used in making said prepolymers is preferably a lowmolecular weight polyoxyalkylene polyol, but may also be a low molecularweight non-polymeric polyol, polyester, or polyetheramide containingreactive hydroxyl groups. Polyols having a molecular weight up to about5,000 are useful. A polyol with a hydroxyl equivalent weight betweenabout and 1,000 (i.e., one active OH group per 130 to 1,000 molecularweight of polyol) is preferred.

Examples of the preferred polyoxyalkylene polyols useful in forming theisocyanate prepolymer are polyoxyethylene polyols, polyoxypropylenepolyols, or polyoxybutylene polyols, such as the glycols represented bythe formula: HO(RO),,H, where (R0), is polyoxyalkylene, for example,polyoxypropylene. Other useful polyoxyalkylene polyols are thecondensates of ethylcne, propylene or butylene oxides withpentaerythritol, sorbitol, sucrose, methylglycocides, or low molecularweight polyols, such as propylene glycol, tri', tetra-, penta-,hexamethylene glycols, 1,3-butylene glycol, 1 ,3-(2-ethyl)hexanediol,2,2,4-trimethyl- 1,3 pentanediol, trimethylolpropane, or1,2,6-hexanetriol. The low molecular weight polyols mentioned above canalso be used and preferably blended with polymeric polyols as componentsin the reaction mixture. Useful polyester polyols include castor oil,derivatives thereof, and those generally prepared by the esterificationreaction of an organic dicarboxylic acid or anhydride thereof with analkylene oxide polyol such as propylene or butylene oxide polyols. Theacid or anhydride may be selected from a wide variety of polybasicacids, such as malonic or succinic acids or prepared by dimerization ortrimerization of unsaturated fatty acids with 18 carbon atoms. Thereactants are combined at molecular ratios to providehydroxyl-terminated groups on the polyester molecules.

The dialkylaminoalkylurethane catalysts of this invention can beprepared by reacting precursor N,N- dialkylalkanolamines withisocyanate-terminated ure thane prepolymers. TheN,N-dialkylalkanolamines useful as precursors in the preparation of suchcatalysts have the structure:

where R is lower alkyl having 1-6, preferably 1-4, carbon atoms and R islower alkylene having 2-5, preferably 2-3, carbon atoms. The preferredN,N-

dialkylalkanolamines are N,N-dimethyl or diethyl ethanolamines or theN,N-dimethyl or diethyl propanolamines. When a larger alkyl group issubstituted on the nitrogen atom or if higher homologous alkanols areused, the catalyst efficiency at elevated temperatures decreases and theperiod of room temperature latency gradually shortens as the length ofthe alkyl or alkylene moieties increases. Also, the higher homologousalcohols provide a catalyst of reduced activity which results in curedisocyanurate resins having substantially less cross-linking than thoseresulting from the use of the catalysts derived from the preferreddialkylalkanolamines. The hydroxyl group of the dialkanolamines offormula [I reacts with an isocyanate group of the isocyanate-terminatedprepolymers of formula I to form a urethane linkage, thus providingdialkylaminoalkylurethanes having a formula:

where R" is the isocyanate-free residue of the isocyanate-terminatedprepolymer of formula I, x is an integer equal to the number ofisocyanate moieties of said prepolymer which reacted with the hydroxylgroup of the alkanolamine of formula I] to form urethane linkages, xbeing at least one, and a is the number of unreacted or remainingisocyanate moieties in said prepolymer. The sum of a plus x is equal tothe product of z multiplied by p. The integer x can be one or can be ashigh as the number of isocyanate moieties present in the prepolymer;however, where the catalyst is prepared in situ, as discussedhereinafter, x will generally be l or 2 since in said in situpreparation, the alkanolamine is reacted with a large excess ofisocyanateterminated prepolymer.

lt is the combination of the urethane linkage and the tertiary aminomoiety in the same molecule that provides the room temperature latencycombined with ac celerated activity at elevated temperature of thepresent invention catalyst as compared to tertiary amines per se,tertiary amine compounds in combination with urethane co-catalysts, ortertiary amine per se compounds in combination with other materials,e.g., esters or ureas.

The catalyst of this invention can be performed by reactingstoichiometric amounts of dialkylalkanolamine with anisocyanate-terminated urethane prepolymer. Alternatively, the catalystof this invention can be formed in situ by adding, for example, 0.1 toweight percent dialkylalkanolamine to the isocyanateterminatedprepolymer to be trimerized or to a mixture of the polyol andpolyisocyanate precursors of said prepolymer to be trimerized. Where apolyolpolyisocyanate reaction mixture is used, the polyolpolyisocyanateand dialkylalkanolamine react at room temperature producing a latentcatalyst of formula III and an isocyanate-terminated prepolymer whichwill trimerize at elevated temperatures formingpolyisocyanurate-urethane.

In general, it is preferred to form the catalyst in situ since thisrequires less processing and the dialkylalkanolamine is chemicallybonded into the resulting polyisocyanurate-urethane eliminating anyobjectionable odor associated with the amine moiety.

When the urethane linkage in the catalyst of this invention is derivedfrom an aromatic isocyanate, i.e., where the nitrogen atom of theurethane linkage in formula ii] is bonded to a ring carbon atom of anaromatic nucleus, a catalyst results which has greater activity atelevated temperatures as well as having a desirable latency at roomtemperature. Catalysts where the urethane linkage is derived fromaliphatic isocyanates, e.g., octylisocyanate, have both a roomtemperature latency and an activity at high temperature intermediatebetween those of known trialkylamine catalysts and the catalyst of thisinvention derived from aromatic isocyanates.

The amount of catalyst used in trimerizing the polyisocyanate orpolyol-polyisocyanate reaction mixtures in accordance with thisinvention will vary depending upon the particular catalyst used and thedesired activity of the catalyst. Generally, the amount of catalyst usedwill be less than 10 weight percent, e.g., 0.5 to 5 weight percent, ofthe isocyanate-terminated prepolymer reactant (or polyol-polyisocyanatemixture) to be trimerized. Functionally stated, the amount of catalystused will be that amount sufficient to catalyze the polymerization ortrimerization of the prepolymer or polyol-polyisocyanate reactionmixture at the desired curing temperature. The desired amount ofcatalyst is mixed with the isocyanate prepolymer or polyolpolyisocyanatemixture at room temperature thereby forming a latently curable reactionmixture which is heated later when desired to activate the catalyst andeffect a rapid cure.

When used in combination with an epoxy compound as co-catalyst, thedialkylaminoalkylurethane catalyst of this combination, while retaininggood room temperature latency, provides a faster and more complete cureat elevated temperatures.

The organic epoxy compounds useful as co-catalysts for the practice ofthis invention are those which typically contain one or more epoxygroups, which have the structure Such compounds, broadly called vicinalepoxides, include epoxy compounds and epoxides of the polymeric type andcan be aromatic, aliphatic, cycloaliphatic or heterocyclic and willtypically have an epoxy equivalency (i.e., the number of epoxy groupscontained in the average molecule) of from preferably l-3. Such epoxidesare well-known and include epihalohydrins, such as epichlorohydrin;alkylene oxides, such as butyl ene diepoxide or styrene oxide; andglycidyl ethers, such as the diglycidyl ether of a polypropylene oxidediol or an epoxy-novolac resin. A list of commercially available epoxycompounds suitable for use in this invention can be found inEncyclopedia of Polymer Science and Technology, V. 6, page 2 l8,lnterscience Pub., New York, (1967). In general, it is preferable to usean epoxy co-catalyst with a high boiling point to prevent loss byevaporation during the curing reaction. Theamount of the epoxy compoundused will vary with the type of epoxy chosen, the polyisocyanate beingtrimerized, and the rate of cure desired; generally amounts of epoxyco-catalyst in the range of 0.001 percent to 5 percent by weight,preferably 0.005 to 2 percent by weight. of the isocyanate-terminatedprepolymer (or polyolpolyisocyanate mixture) to be trimerized aresufficient to impart improved cure rates.

The NCO-terminated prepolymers trimerized with the catalyst of thisinvention to produce urethanemodi- 5 fied polyisocyanurates are known(e.g. see US. Pat. No. 3.054,755) and are generally prepared by reactingan excess of polyisocyanate, such as an aromatic diisocyanate, withpolyoxyalkylene polyols. or polyester polyols as hereinbefore described.The prepolymers to be trimerized preferably have the same structure asthat shown in formula 1 above.

The polyol used to form the isocyanate-terminated prepolymers to betrimerized is preferably a low molecular weight polyoxyalkylene polyol,but may also be a low molecular weight non-polymeric polyol, or apolyester or polyether amide containing reactive hydroxyl groups.Polyols having a molecular weight up to about 5,000 are useful. A polyolof hydroxyl equivalent weight between about I30 and 1000 (i.e.. oneactive OH group per 130 to 1,000 molecular weight of polyol) ispreferred. Polyols useful in preparing the prepolymers to be trimerizedinclude those discussed hereinbefore in the preparation of the catalystof this invention. Where softer polyisocyanurate reaction products aredesired. the polyol may have one reactive OH group per 400 to 1.000atomic weight units of polymer. The rubbery polyisocyanurate productspreferably should have a cross-linked density of about one isocyanuratecross-link per 2,000 to 20,000 atomic weight units, while the more rigidproducts have a cross-link density of about one cross-link per 400-2,000atomic weight units.

Generally. the polyol-polyisocyanate reaction mixtures cured with thecatalyst of this invention can have NCO/OH equivalent ratios in therange of l/] to 12/1, and even higher, e.g., 20/1, preferably at least1.2/1 since below the latter. the polyisocyanurate product will containunreacted or free hydroxyl groups (which have a plasticizing function)and will be a more flexible product. Products made from reactionmixtures having NCO/OH ratios of l/l to 1.2/1 can be characterized asisocyanurate-modified polyurethanes, the isocyanurate content generallybeing at least 1.0 weight percent of the product. Those products madefrom reaction mixtures with NCO/OH ratios of 1.2/1 and greater. e.g.,3/l-l2/l, can be characterized as urethane-modified polyisocyanurates.the isocyanurate content being generally at least 5.0 weight percent ofthe product. The

preferred products are those which are highly crosslinked by reason ofhaving -80 percent of the NCO groups of the polyisocyanate reactantconverted into isocyanurate linkages. In general, regardless of theNCO/OH ratio. the mixed polyisocyanuratepolyurethane products of thisinvention have an amount of isocyanurate linkage in the polymer backbonesufficient to provide a heat stable product, Le. a product which retains75-100 percent of its room temperature hardness when heated at elevatedtemperatures, eg. one hour at 300-500 F.

Where a higher cross-linked or chain-extended product is desired. theisocyanate-terminated prepolymer can be formed from apolyol-polyisocyanate reaction mixture which includes a conventionaltrifunctional or polyfunctional isocyanate or a trio]. The reactionmixture can also include modifying mono-isocyanates or alcohols, such as1,4-butanediol, butyl-cellosolve, butylcarbitol, etc.. to impart specialproperties to the polymer product, such as the degree of hardness.

Curing of the isocyanate-terminated prepolymers in the presence of thecatalyst of this invention is generally carried out at an elevatedtemperature, generally in the range of 40-1 75 C., preferably within therange of 90-l50 C., and usually takes place in 100 minutes or less atthese temperatures. The rate of curing will be influenced by thedialkylalkanolamine precursor chosen in making thedialkylaminoalkylurethane catalyst as well as the polyisocyanate and thecuring temperature and catalyst concentration. This is in contrast topreviously known catalysts which do not provide accelerated curing ratesat elevated temperatures combined with catalyst latency at roomtemperature.

Objects and advantages of this invention are illustrated in thefollowing examples, but the various materials and amounts described inthese examples. and various other conditions and details recited thereinshould not be construed to limit the scope of this invention. All partsare by weight unless otherwise specified.

EXAMPLE I A liquid isocyanate-terminated urethane prepolymer wasprepared by stirring for a period of 24 hours a mixture comprising 210grams of polymethylene polyphenyl isocyanate (Mondur MRS," having anequivalent weight of 135) and grams of polypropylene oxide diol havingan equivalent weight of 1000. Infrared analysis indicated all of thehydroxyl groups had reacted with polyisocyanate to form urethanelinkages. In a plurality of runs, duplicate samples of the resultingisocyanate-terminated prepolymer were mixed with various tertiary aminesby blending l-5 percent by weight of the amines. The latency (i.e., curetime at room temperature) of one set of samples was observed andrecorded. The other set of duplicate samples were heated in a warm airoven at about 135 C. and periodic observations made, until thepolyisocyanurate resin was firm and nontacky. The runs and results aresummarized in Table 1.

TABLE 1 Shore D hard- Run Tertiary amine added Cure time at room Curetime ness of poly- No. to polyisocyanate temperature at 135 C.lsocyanurate l (CH ),NCH,CH,OH 49-56 days 21-27 min. 87 2 (CH),NCH,CH,CH OH 30-31 days 42-48 min. 88

(|)H tCHmNCH CHCH 80-90 days 24-30 min. 37 4 (C,H,) NCH CH,OH 52-58 daysl2-24 m n. 5 (C H ),NCH,CH,OH 51-58 days 25-30 m n. 6 H,,),NCH,CH,CH,OH30-35 days 15-35 mm. 82

O H" v 7 C H NCOCH CmNrCH- -[00 days 78-96 min. as 8 [CH, )-,N(CH; ,OH7-10 days l20-l50 min. 20

TABLE 1 (ontinued Shore D hard- Run Tertiary amine added Cure time atroom Cure time ness of poly- No. to polyisocyanutc temperature at 135 C.isocyanurate OH I 9 (CH NCH CHCH,OH 87-96 days 2 hrs. bubbled 1t) Cl'lN[CH CH OHl 90-100 days 411-511 m n. bubbled ll N(CH CH OH]; 90-1110days fill-)5 mm. 45

12 R R 7-22 hrs. 7 hrs. too soft to measure where R is Ca men l3Dimethylbenzylamine (10 days 7 hrs. 14 Dimcthyldodecylamine 21-24 days 6hrs. l5 l5 Dimethylcyclohcxylaminc 5-6 days 7 hrs. 12 l6 1CH ),NCHCH,N(CH 15-18 days 7 hrs. too soit to measure 17 (CH ),NCH CH CN 50 days7 hrs. too soft to measure 0 ll 18 Q-cuacmcmmcam 31-36 days 2 lll'S. so

0 ll 19 QP-COCH CH- MCHQ 100-110 days 8 hrs. 10

i 20 CH;,COCH,CH,N(CH 90-100 days 8 hrs. 10 2| (CH ),NCH,CH,NH 12-15days 3 hrs. too soft to measure Dimethylcyclohexyl 2-3 days 105-195 mm.

Runs 1 l 0 show the results obtained using various hydroxy tertiaryamines to form various urethanes in situ, with Runs 1-6 being thedialkylalkanolamine precursors used in making the catalyst of thisinvention. The catalyst of Runs 1-6 is shown to have a room tempera turelatency of at least days, coupled with accelerated cure rates at 135 C.of less than 60 minutes, and thus are demonstratably better than thecatalyst used in the other runs. Runs 1 1-17 show the effectiveness ofknown amines having utility for trimerizing isocyanate, while Runs 18-21show the effects of using a tertiary amine compound lacking a urethanemoiety in the same molecule. Run 22 is similar to those mixturesdisclosed in U.S. Pat. No. 2,954,365.

The cross-linking of the cured polyisocyanurate resins in Runs 1-6 isnoticably higher than that of the other amines as shown by Shore Dhardness of greater than 70. The low level of cross-linking of Runs 8-22is indicated by the Shore D hardness of 60 or less measured on the curedsamples. Such a low level of cross-linking makes products formed usingthese catalyst less desirable where a hard, tough, cross-linked materialis desired.

The poly(isocyanurate-urethane) resins formed using thedialkylaminoalkyl-urethane catalysts of this invention demonstrate theirutility in obtaining fast cure rate and high level of cross-linking atelevated temperature while having good room temperature latencyv EXAMPLE11 By a procedure similar to that described in Example 1, 8.1 gramsofMondur MRS polyisocyanate was re acted with 1.8 gramsN,N-dimethylethanolamine to provide a catalyst falling within the scopeof formula 1 where R" is the polymethylene polyphenyl residue of LIIEXAMPLE 111 Two reaction mixtures were formed with the follow ingcompositions:

Mixture A Mixture B parts isocyanatcterrninated 100 partsisocyanate-terminated prepolymer prepolymer" 1 part HOCH,CH N(CH 1 partN,N-dimethylcyclohexylamine 1 part polypropylene oxide diglycidyl ether"1 part polypropylene oxide diglycidyl ether 'prepolymer used was thatdescribed in Example 1 "Dl-IR 736 having an equivalent weight of -205After mixing, each formulation was allowed to stand at ambient roomtemperature of about 25 C. After 20 hours, the bulk viscosities of themixtures were measured by means ofa Brookfield viscometer with thefollowing results:

Mixture Viscosity A 1 3 .900 centipoises B 58.300 centipoisesFormulation B was solid when examined after standing at ambienttemperature 24 hours while formulation A was still fluid when examined 3days later. This demonstrates even with a co-catalyst, such as epoxy,the tertiary amino urethane systems of this invention retain roomtemperature latency for several days.

EXAMPLE [V ture required several hours to cure at 135 C. while the roomtemperature latency was only 1-2 days.

EXAMPLE VII 5 The isocyanate-terminated prepolymer described inAdiprene" L-l67, a polytetramethylene oxide diol Example l was cured at135 C. using various amines end-capped with tolylene diisocyanate,having 6-7 added to the prepolymer as catalysts or reacted in situweight percent NCO, was mixed with 2 weight percent to form thedialkylaminoalkylurethane of this inven- N,N-dimethylethanolamine andthe mixture was heated tion. Vinylcyclohexene dioxide was used as anepoxy to about 135C. for about minutes. The isocyanatel0 co-catalyst. inRun 1, the N,N-dimethylethanolamine terminated polymer cured to aflexible poly(urethanewas used at one percent by weight of theisocyanate isocyanurate) rubber having a Shore A hardness of 50.prepolymer. The other runs used an amount of catalyst A portion of thereaction mixture kept at room temperequivalent to the amine equivalentused in Run l. The ature, about 25 C., remained fluid for 51-54 days.vinylcyclohexene dioxide was used at a level of 0.1 per- TABLE ll Curetime at room Amine used with vinyl- Cure time Shore D Run temperaturecyclohexene dioxide at 275 F. hardness 1 27-30 daysN.N'dimethylaminoethanol min. 88 2 8-9 days N.N-dimethylcyclohexylamine4 hrs. 52 3 18-21 days N.N-dimethylbenzylamine 3.5 hrs. 35 4 11-14 daysN,N-dimethyldodecylamine 5 hrs. 60

A similar mixture employing N,N-dimcthylcyclohexylamine as the catalystrequired about 2 hours at 135 C. to cure completely; the resultingpoly(urethaneisocyanurate) had a Shore A hardness of 45. A portion ofthis reaction mixture kept at room temperature solidified in 5-6 days.

EXAMPLE V An isocyanate-terminated prepolymer was prepared by stirring66 parts tolylene diisocyanate, 18 parts of polypropylene oxide diolhaving an equivalent weight of 1,000, and 16 parts tripropylene glycol.A sample of the isocyanate-terminated polymer was blended with 2 weightpercent N,N-dimethylethanolamine and cured at 95 C. in -35 minutesgiving a cured poly(urethane-isocyanurate) resin having a Shore Dhardness of 917 A portion of the reaction mixture remained fluid atambient room temperature for more than 7 days.

The same isocyanate-terminated polymer mixed withN,N-dimethylcyclohexylamine required 50-56 minutes to cure at 95 Cv Theresulting resin was quite brittle and had a Shore D hardness of 50. Aportion of the reaction mixture solidified in about 24 hours at ambientroom temperature.

EXAMPLE VI A mixture comprising 70 parts polymethylene polyphenylisocyanate having an equivalent weight of 135, 30 parts polypropyleneoxide diol having an equivalent weight of 1,000. and 2 parts N,N-dimethylethanolamine was stirred for 5 minutes at room temperature.During the stirring, the mixture became slightly warm. lnfrared analysisindicated essentially all of the hydroxyl groups had reacted to formurethane linkages. A portion of the mixture was heated at about 135 C.for 30 minutes. A bubble-free poly- (urethane-isocyanurate) having aShore D hardness of 86 was obtained after curing. A portion of thereaction mixture kept at ambient room temperature remained fluid formore than days.

A similar polyisocyanate-polyol mixture was catalyzed usingN.N-dimethylcyclohexylamine in place of N,N-dimethylethanolamine.Urethane linkages also formed within a few minutes; however, the secondmixcent by weight of the isocyanate prepolymer. The results aretabulated in Table II:

The dialltylaminoalkylurethane catalyst formed by Run 1 displays betterroom temperature latency. combined with a faster cure and a greaterdegree of cross-linking even when an epoxy-containing compound ispresent.

EXAMPLE VIII The isocyanate-terminated polymer of Example V was blendedwith one percent by weight N,N dimethylethanolamine and 0.05 percent byweight polypropylene oxide diglycidylether having an equivalent weightof 175-205. Heating the resulting mixture at C. cured theisocyanate-terminated polymer in 21-24 minutes to apoly(urethane-isocyanurate) with a Shore D hardness of 88. At roomtemperature, the reaction mixture remained fluid for more than 24 hours.In similar runs. substituting N,N-dimethylcyclohexylamine forN,N-dimethylethanolamine, curing at 105 C. required 50-55 minutes andthe Shore D hardness of the resulting resin was only 70. At roomtemperature, the reaction mixture remained fluid for only 6 hours.

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scope orspirit of this invention, and it should be understood that thisinvention is not to be limited to the illustrative embodiments set forthherein.

What is claimed is:

l. A dialkylaminoalkylurethane of the structure:

where R" is the isocyanate-free residue of an isocyanateterminatedprepolymer, R is lower alkylene having 2-5 carbon atoms, R is loweralltyl having l-6 carbon atoms, x is an integer of at least one, and ais zero or an integer of at least one.

2. The dialliylaminoalkylurethane according to claim I where R is loweralkyl having l-3 carbon atoms and R is lower alkylene having 2-3 carbonatoms.

12 polyisocyanate.

6. The dialkylaminoalkylurethane of claim 1 wherein said prepolymer isthe reaction product of a polyoxyalkylene polyol and an excess of anaromatic polyisocyanate R is methyl, R' is ethylene, and the urethanemoiety shown in the structural formula is bonded to a ring carbon atomof an aromatic nucleus.

1. A DIALKYLAMINOALKYLURETHANE OF THE STRUCTURE:
 2. Thedialkylaminoalkylurethane according to claim 1 where R is lower alkylhaving 1-3 carbon atoms and R'' is lower alkylene having 2-3 carbonatoms.
 3. The dialkylaminoalkylurethane according to claim 1 where R ismethyl and R'' is ethylene.
 4. The dialkylaminoalkylurethane accordingto claim 1 wherein the urethane moiety shown in the structural formulais bonded to a ring carbon atom of an aromatic nucleus.
 5. Thedialkylaminoalkylurethane according to claim 1 wherein said prepolymeris the reaction product of a polyoxyalkylene polyol and an excess of anaromatic polyisocyanate.
 6. The dialkylaminoalkylurethane of claim 1wherein said prepolymer is the reaction product of a polyoxyalkylenepolyol and an excess of an aromatic polyisocyanate, R is methyl, R'' isethylene, and the urethane moiety shown in the structural formula isbonded to a ring carbon atom of an aromatic nucleus.